Oracle体系结构及备份(十五)bg-lgwr
一 什么是LGWR进程 LGWR写的条件: 提交的时候 达到三分之一满 日志的大小达到1M 每隔三秒 在DBWn进程写之前 The log writer process writes redo logentries to disk. Redo log entries are generated in the redo log buffer of thesystem global area (SG
一 什么是LGWR进程
LGWR写的条件:
提交的时候
达到三分之一满
日志的大小达到1M
每隔三秒
在DBWn进程写之前
The log writer process writes redo logentries to disk. Redo log entries are generated in the redo log buffer of thesystem global area (SGA). LGWR writes the redo log entries sequentially into aredo log file. If the database has a multiplexed redo log, then LGWR writes theredo log entries to a group of redo log files.
二 操作示例
[oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgw oracle 6446 1 0 11:15 ? 00:00:00 ora_lgwr_orcl [oracle@localhost 桌面]$ kill -9 6446 [oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgw [oracle@localhost 桌面]$ ps -ef | grep ora_ oracle 6486 2720 0 11:17 pts/0 00:00:00 grep ora_ [oracle@localhost 桌面]$ sqlplus / as sysdba; SQL*Plus: Release 10.2.0.1.0 - Production on Thu Jun 6 11:17:45 2013 Copyright (c) 1982, 2005, Oracle. All rights reserved. Connected to an idle instance. SQL> startup ORACLE instance started. Total System Global Area 838860800 bytes Fixed Size 1222192 bytes Variable Size 788531664 bytes Database Buffers 46137344 bytes Redo Buffers 2969600 bytes Database mounted. Database opened. SQL> show parameter log_buff; NAME TYPE VALUE ------------------------------------ ----------- ------------------------------ log_buffer integer 2923520 SQL> exit; Disconnected from Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Production With the Partitioning, OLAP and Data Mining options [oracle@localhost 桌面]$ ps -ef | grep ora_ | grep lgw oracle 6499 1 0 11:17 ? 00:00:00 ora_lgwr_orcl [oracle@localhost 桌面]$ ps -ef | grep ora_ oracle 6491 1 0 11:17 ? 00:00:00 ora_pmon_orcl oracle 6493 1 0 11:17 ? 00:00:00 ora_psp0_orcl oracle 6495 1 0 11:17 ? 00:00:00 ora_mman_orcl oracle 6497 1 0 11:17 ? 00:00:00 ora_dbw0_orcl oracle 6499 1 0 11:17 ? 00:00:00 ora_lgwr_orcl oracle 6501 1 0 11:17 ? 00:00:00 ora_ckpt_orcl oracle 6503 1 0 11:17 ? 00:00:00 ora_smon_orcl oracle 6505 1 0 11:17 ? 00:00:00 ora_reco_orcl oracle 6507 1 0 11:17 ? 00:00:00 ora_cjq0_orcl oracle 6509 1 0 11:17 ? 00:00:00 ora_mmon_orcl oracle 6511 1 0 11:17 ? 00:00:00 ora_mmnl_orcl oracle 6513 1 0 11:17 ? 00:00:00 ora_d000_orcl oracle 6515 1 0 11:17 ? 00:00:00 ora_s000_orcl oracle 6519 1 0 11:17 ? 00:00:00 ora_qmnc_orcl oracle 6525 1 0 11:18 ? 00:00:00 ora_j000_orcl oracle 6527 1 0 11:18 ? 00:00:00 ora_q000_orcl oracle 6529 1 0 11:18 ? 00:00:00 ora_q001_orcl oracle 6535 2720 0 11:18 pts/0 00:00:00 grep ora_
三 总结
1.LGWR,将重做日志有序地写入重做日志文件中。
2.LGWR写的条件:提交的时候、达到三分之一满、日志的大小达到1M、每隔三秒、在DBWn进程写之前。
3. Log buffer:通过LGWR进程写入到logfile中。
4.Linux中同样使用ps命令查看进程。
<span><span>我的邮箱</span></span><span>:</span>wgbno27@163.com <span> <span>新浪微博</span></span><span>:</span>@Wentasy27 <span>微信公众平台</span>:JustOracle(微信号:justoracle) <span>数据库技术交流群</span>:336882565(加群时验证 From CSDN XXX) <span>Oracle交流讨论组</span>:https://groups.google.com/d/forum/justoracle <span><strong>By Larry Wen</strong></span>Copy after login
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